If you absolutely HAVE to get a few cories...I recommend the pygmy cories. There are 3 different species: Pygmaeus/Hastatus/Hasbrosus. They won't grow any bigger then the neons. You can probably get 2 or 3...IF... you have good filtration, and some experience in fishkeeping (1-2 years).
If you are a beginner...I wouldn't get any more fish.
